UnratedApache Software Foundation

Advisory [CVE-2026-24281] Apache ZooKeeper: Reverse-DNS fallback enables hostname verification bypass in ZooKeeper ZKTrustManager

This security Apache Software Foundation advisory covers CVE-2026-24281 affecting Apache ZooKeeper.

CVE-2026-24281 Published Mar 7, 2026Updated by vendor Jul 15, 2026

CVE-2026-24281

Affected products & platforms

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Summary

Hostname verification in Apache ZooKeeper ZKTrustManager falls back to reverse DNS (PTR) when IP SAN validation fails, allowing attackers who control or spoof PTR records to impersonate ZooKeeper servers or clients with a valid certificate for the PTR name.

It's important to note that attacker must present a certificate which is trusted by ZKTrustManager which makes the attack vector harder to exploit. Users are recommended to upgrade to version 3.8.6 or 3.9.5, which fixes this issue by introducing a new configuration option to disable reverse DNS lookup in client and quorum protocols.

Affected versions

Apache ZooKeeper 3.9.0 through 3.9.4
Apache ZooKeeper 3.8.0 through 3.8.5

Official advisory · medium-confidence parse· fetched 2 months ago·verify at source

Fixed versions

3.8.6
3.9.5

Official advisory · medium-confidence parse· fetched 2 months ago·verify at source

Mitigation checklist

Temporary workarounds

Users are recommended to upgrade to version 3.8.6 or 3.9.5, which fixes this issue by introducing a new configuration option to disable reverse DNS lookup in client and quorum protocols.

Official advisory · medium-confidence parse· fetched 2 months ago·verify at source

Sources

Official and corroborating records used to build this advisory.

Official vendor advisoryofficial
Official advisory page fetched and parsed for the summary, affected/fixed versions and remediation guidance it provides.
Apache Software Foundation
CVE.org CNA recordCVE.org
Independent CNA record used for near-real-time discovery and missed-CVE reconciliation. Discovered from the machine-readable feed https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/delta.json; this link opens the CVE.org record for CVE-2026-24281 instead of the raw feed document.
CVE Program

Cross-references

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CVE-2026-24281NVD CVE.org MITRE

Official resources

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